1. Field of the Invention
This invention relates to a method for coating an article with a thermoplastic coating, more especially a polyolefin composition, containing an ionomer, and to the article produced thereby. More particularly, this invention relates to a method of applying a polyolefin polymer or copolymer coating, more specifically a polyethylene coating, containing an ionomer to a metal surface, such as the inner surface of a metal pipe, to provide an article having a strongly adherent protective coating.
2. Description of the Prior Art
It is well known to coat articles with thermoplastic materials for protection against corrosion and various other purposes. Polyethylene compositions have been used extensively in the coating of metal articles, such as the lining of tanks and chemical equipment, the inner surfaces of pipes, etc. For example, U.S. Pat. No. 4,007,298 discloses a method of coating metal articles with a blend of high and low density polyethylene powders. While various prior art polyethylene coatings have displayed fairly satisfactory adhesion to metal substrates, under certain environmental conditions these coatings become subject to underfilm corrosion (so-called "undercutting"). This "undercutting" phenomenon is most evident at places where, due to the coating's cracking or stripping, the substrate or body of the coated article becomes exposed to the corrosive environment in which the article is used.
It would be highly desirable if an improved method of applying a thermoplastic material to a substrate could be found which is relatively simple and inexpensive to perform and yields a highly adherent and corrosion-resistant coating.